Ultrasound imaging apparatus and method of controlling the same

ABSTRACT

Disclosed herein are an ultrasound imaging apparatus and a method for controlling the same. An occluded region generated in a 2D image may be removed by performing frame interpolation on a surface region of an object by extracting the surface region of the object from 3D ultrasonic volume data and calculating a motion vector in the extracted surface region, and an amount of calculation may be reduced by calculating a motion vector of the surface region in 3D volume data. The ultrasound imaging apparatus includes a volume data generator configured to acquire volume data which relates to the object, a surface region extractor configured to extract the surface region of the object based on the acquired volume data, and a frame interpolator configured to perform frame interpolation on the extracted surface region of the object.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority from Korean Patent Application No.10-2014-0107732, filed on Aug. 19, 2014 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

Exemplary embodiments relate to ultrasound imaging apparatusesperforming frame interpolation only on a surface region of a 3Dultrasound image by extracting the surface region and methods forcontrolling the same.

2. Description of the Related Art

Ultrasound diagnostic apparatuses non-invasively generate an image of atarget region inside an object, such as a soft tissue tomogram or ablood stream tomogram, by irradiating ultrasonic signals generated bytransducers of a probe toward the target region from the surface of theobject, and receive reflected ultrasonic signals (ultrasonic echosignals), which are used for medical purposes, for example, to examinethe inside of the object, detect impurities, and measure injury.

Since ultrasound diagnostic apparatuses are small and inexpensive,display an image in real time, and provide high safety without causingX-ray exposure, as compared to other diagnostic imaging apparatuses,such as X-ray diagnosis apparatuses, computed tomography (CT) scanners,magnetic resonance imaging (MRI) apparatuses, and nuclear medicinediagnosis apparatuses, the ultrasound diagnostic apparatus have beenwidely used with other diagnostic imaging apparatuses.

With the recent expansion of use of ultrasound systems, variousrequirements for ultrasound images provided by the ultrasound systemsare continuously increasing. In particular, since precise examination oflesions and tissues of patients are required for medical treatments suchas examination, biopsy, and surgery, ultrasound systems must be able toacquire multifocal ultrasound images.

However, when a multifocal ultrasound image is acquired, a frame rate ofthe ultrasound image provided by an ultrasound system may considerablydecrease. Accordingly, in a medical treatment requiring real timeultrasound images, natural ultrasound images cannot be provided.

In addition, it is difficult to acquire natural ultrasound volume imagesof a fetus due to a low frame rate.

Thus, a technique of increasing the number of frames and frame rate isused by frame interpolation. In this regard, when frame interpolation isperformed on a 2D image by using a motion vector, an occluded regionthat is hidden by motion or movement of the fetus may be generated.Although all tissues may be identified via a 3D image without causing anoccluded region when volume interpolation is performed on 3D volume databy using a motion vector, an amount of calculation increases due tocalculation of a motion vector of V*V*V from a volume of N*N*N.

Thus, there is a need to develop a method of performing frameinterpolation by calculating a motion vector without causing an occludedregion to reduce the amount of calculation.

SUMMARY

Therefore, it is an aspect of one or more exemplary embodiments toprovide an ultrasound imaging apparatus and a method for controlling thesame. An occluded region caused when using a 2D image may be removed byperforming frame interpolation in a surface region of an object byextracting the surface region of an object from 3D ultrasound volumedata and calculating a motion vector of the surface region. An amount ofcalculation may be reduced by calculating a motion vector of the surfaceregion of 3D volume data.

Additional aspects of the exemplary embodiments will be set forth inpart in the description which follows and, in part, will be apparentfrom the description, or may be learned by practice of the exemplaryembodiments.

In accordance with one aspect of one or more exemplary embodiments, anultrasound imaging apparatus includes a volume data generator configuredto acquire volume data which relates to an object, a surface regionextractor configured to extract a surface region of the object based onthe acquired volume data, and a frame interpolator configured to performframe interpolation on the extracted surface region of the object basedon the calculated motion vector.

The ultrasound imaging apparatus may further include a motion vectorcalculator configured to calculate a motion vector in the extractedsurface region of the object.

The motion vector calculator may include an occluded region motionvector calculator configured to calculate a motion vector of an occludedregion.

The occluded region may include a region which corresponds to a timedifference between a first predetermined time and a second predeterminedtime in the surface region of the object.

The occluded region may include a region generated when the frameinterpolation is performed.

The motion vector calculator may be further configured to calculate themotion vector by comparing volume data which relates to the firstpredetermined time with volume data which relates to the secondpredetermined time.

The occluded region motion vector calculator may be further configuredto calculate the motion vector of the occluded region simultaneouslywith calculating the motion vector in the surface region of the object.

The motion vector calculator may include a surface region and motionvector tracker configured to track a surface region and a motion vectorof a predetermined frame.

The surface region and motion vector tracker may be further configuredto track the surface region and the motion vector of the predeterminedframe based on data which relates to the extracted surface region andthe calculated motion vector.

The motion vector calculator may be further configured to calculate amotion vector of a subregion of a frame.

The surface region extractor may be further configured to extract asurface region of at least one from among an outline of a fetus and anorgan such as a heart.

In accordance with another aspect of one or more exemplary embodiments,a method for controlling an ultrasound imaging apparatus includesacquiring volume data which relates to an object, extracting a surfaceregion of the object based on the acquired volume data, and performingframe interpolation on the extracted surface region of the object.

The method may further include calculating a motion vector in theextracted surface region of the object.

The calculating the motion vector on the extracted surface region of theobject may include calculating a motion vector of an occluded region.

The occluded region may include a region which corresponds to a timedifference between a first predetermined time and a second predeterminedtime in the surface region of the object.

The occluded region may be generated when the frame interpolation isperformed.

The calculating the motion vector in the surface region of the objectmay be performed by calculating a motion vector by comparing volume datawhich relates to the first predetermined time with volume data whichrelates to the second predetermined time.

The calculating the motion vector of the occluded region may beperformed simultaneously with calculating the motion vector in thesurface region of the object.

The calculating the motion vector in the surface region of the objectmay include tracking a surface region and a motion vector of apredetermined frame.

The tracking the surface region and the motion vector of thepredetermined frame may be performed by tracking a surface region and amotion vector of the predetermined frame based on data which relates tothe extracted surface region and the calculated motion vector.

The object may include a fetus, and the extracting the surface region ofthe object may be performed by extracting a surface region of at leastone from among an outline of the fetus and an organ such as a heart.

The calculating the motion vector of the surface region of the objectmay be performed by calculating a motion vector of a subregion of aframe.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of exemplary embodiments,taken in conjunction with the accompanying drawings of which:

FIG. 1 is a perspective view illustrating an ultrasound imagingapparatus, according to an exemplary embodiment;

FIG. 2 is a control block diagram illustrating an ultrasound imagingapparatus, according to an exemplary embodiment;

FIG. 3A is a diagram illustrating a plurality of 2D cross-sectionalimages;

FIG. 3B is a diagram illustrating volume data;

FIG. 4 is a block diagram illustrating a controller of an ultrasoundimaging apparatus, according to an exemplary embodiment;

FIG. 5 is a diagram for describing an occluded region that is screenedby a motion in a 2D image;

FIG. 6 is a flowchart illustrating a method of controlling an ultrasoundimaging apparatus by which a surface region and a motion vector of thenext frame are not tracked;

FIG. 7 is a flowchart illustrating a method of controlling an ultrasoundimaging apparatus by which a surface region and a motion vector of thenext frame are tracked;

FIG. 8 is an ultrasound image showing a region to extract the surfaceregion of an object, according to an exemplary embodiment;

FIGS. 9A and 9B are diagrams for describing a calculation of a motionvector of a surface region of an object having an occluded region;

FIG. 10A is a diagram for describing virtual images generated by frameinterpolation;

FIG. 10B is an example of virtual images generated by frameinterpolation;

FIG. 11 illustrates ultrasound images indicating frame interpolation ata predetermined time, according to an exemplary embodiment; and

FIG. 12 illustrates ultrasound images indicating frame interpolation atconsecutive times, according to an exemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to likeelements throughout.

Hereinafter, an ultrasound imaging apparatus and a method forcontrolling the same will be described in detail with reference to thedrawings.

A medical imaging apparatus according to an exemplary embodiment mayrefer to any one or more of an X-ray imaging apparatus, a fluoroscopicX-ray system, a computed tomography (CT) scanner, a magnetic resonanceimaging (MRI) apparatus, a positron emission tomography apparatus, andan ultrasound diagnostic apparatus. Hereinafter, an ultrasound imagingapparatus will be described as a medical imaging apparatus by way ofexample. As used herein, the term ‘ultrasound image’ refers to an imageof an object acquired using ultrasound. As used herein, the term object”refers to human, fetus, animal, metal, non-metal, or a part thereof. Forexample, the object ob may include any one or more of organs such asliver, heart, uterus, brain, breast, and abdomen and/or blood vessels.In addition, the object may also include a phantom. Phantom refers to amaterial that has density, effective atomic number, and volume similarto biological tissues.

As used herein, the term “user” refers to medical professionals such asdoctors, nurses, medical laboratory technologists, medical imagingprofessionals, ultrasound examiners, medical equipment technicians, andthe like, without being limited thereto.

FIG. 1 is a perspective view illustrating an ultrasound imagingapparatus, according to an exemplary embodiment. Referring to FIG. 1,the ultrasound imaging apparatus includes a main body 100, an ultrasoundprobe 110, an input unit (also referred to herein as an “input device”)150, and a display 160.

The main body 100 may be provided with at least one female connector 145at one side thereof. A male connector 140 connected to a cable 130 maybe physically coupled to the female connector 145.

Meanwhile, a plurality of casters (not shown) may be provided at thebottom of the main body 100 in order to enable the ultrasound imagingapparatus to move. The plurality of casters may fix the ultrasoundimaging apparatus at a predetermined place or allow the ultrasoundimaging apparatus to move in a predetermined direction. Such ultrasoundimaging apparatuses are referred to as cart-type ultrasound imagingapparatuses.

Alternatively, the ultrasound imaging apparatus may be a portableultrasound imaging apparatus that may be carried during a long distancejourney, as opposed to that illustrated in FIG. 1. In this regard, theportable ultrasound imaging apparatus may not be provided with casters.Examples of the portable ultrasound imaging apparatus may include any ofa picture archiving and communication system (PACS) viewer, a smartphone, a laptop computer, a personal digital assistant (PDA), and atablet PC, without being limited thereto.

The ultrasound probe 110 that contacts the surface of the body of anobject may transmit and receive ultrasonic signals. In particular, theultrasound probe 110 may transmit ultrasonic signals into the object inaccordance with a signal received from the main body 100, receiveultrasonic echo signals reflected by a specific region of the object,and transmit the received ultrasonic echo signals to the main body 100.

One end of the cable 130 may be connected to the ultrasound probe 110,and the other end of the cable 130 may be connected to the maleconnector 140. The male connector 140 connected to the other end of thecable 130 may be physically coupled to the female connector 145.

Alternatively, differently from FIG. 1, the ultrasound probe 110 may bewirelessly connected to the main body 100. In this case, the ultrasoundprobe 110 may transmit the ultrasonic echo signals received from theobject to the main body 100 in a wireless manner. In addition, aplurality of ultrasound probes may be connected to one main body.

Meanwhile, an image processor 350 that converts ultrasonic echo signalsreceived by the ultrasound probe 110 into an ultrasound image may bemounted in the main body 100. The image processor 350 may be implementedas at least one of a hardware processor, such as a microprocessor,and/or as a software processor executed on a hardware platform.

The image processor may generate an ultrasound image via scan conversionof ultrasonic echo signals. In this regard, the ultrasound image mayinclude not only a gray scale image acquired by scanning the object inan amplitude mode (A mode), a brightness mode (B mode), and a motionmode (M mode), but also a Doppler image representing an image of amoving object by using the Doppler Effect. The Doppler image may includeany of a blood stream Doppler image indicating a flow of blood (colorDoppler image), a tissue Doppler image showing movement of tissues, anda spectrum Doppler image illustrating a speed of a moving object aswaveforms.

The image processor may extract B mode components from the ultrasonicecho signals received by the ultrasound probe 110 in order to generate aB mode image.

Similarly, the image processor may extract Doppler components from theultrasonic echo signal in order to generate a Doppler image in whichmotion of the object is expressed as color or waveforms based on theextracted Doppler components.

Furthermore, the image processor may generate a 3D ultrasound image byperforming volume rendering of volume data acquired by the ultrasonicecho signal, or may generate an elastic image in which the degree ofdeformation of the object by pressure is imaged. In addition, the imageprocessor may express additional information on the ultrasound image byusing texts and graphics.

Meanwhile, the generated ultrasound image may be stored in at least oneof an internal memory of the main body and/or an external memory.Alternatively, the ultrasound image may also be stored in a web storageor a cloud server.

The input unit 150 may receive an instruction related to operation ofthe ultrasound imaging apparatus. For example, the input unit 150 mayreceive an instruction to select a mode such as the A mode, the B mode,the M mode, or the Doppler image mode. The input unit 150 may alsoreceive an instruction to initiate an ultrasonic diagnosis.

The instruction input via the input unit 150 may be transmitted to themain body 100 via a wireless or wired communication network.

The input unit 150 may include at least one of a keyboard, a footswitch, and/or a foot pedal. The keyboard may be a hardware elementlocated at an upper portion of the main body 100. The keyboard mayinclude at least one of a switch, a key, a joystick, and a trackball. Asanother example, the keyboard may include a software element, such as agraphical user interface. In this case, the keyboard may be displayedvia a sub display 161 or a main display 162. The foot switch or footpedal may be provided at a lower portion of the main body 100, and auser may control operation of the ultrasound imaging apparatus by usingthe foot pedal.

The display 160 may include the main display 161 and the sub display162.

The sub display 162 may be provided at the main body 100. FIG. 1illustrates that the sub display 162 is provided on the input unit 150.The sub display 162 may display an application related to operation ofthe ultrasound imaging apparatus. For example, the sub display 162 maydisplay any of menus, guidelines, or the like for ultrasonic diagnosis.Examples of the sub display 162 may include cathode ray tubes (CRTs) andliquid crystal displays (LCDs).

The main display 161 may be provided at the main body 100. FIG. 1illustrates that the main display 161 is provided above the sub display162. The main display 161 may display an ultrasound image acquiredduring the ultrasonic diagnosis in accordance with an input applied viathe input unit. The main display 161 may also include a CRT or a LCDsimilarly to the sub display 162. Although FIG. 1 illustrates that themain display 161 is coupled to the main body 100, the main display 161may also be separately formed from the main body 100.

FIG. 1 illustrates that the ultrasound imaging apparatus includes boththe main display 161 and the sub display 162. However, the sub display162 may not be used. In this case, applications or menus displayed onthe sub display 162 may be displayed on the main display 161.

Meanwhile, the ultrasound imaging apparatus may further include acommunication unit (also referred to herein as a “communicator” and/oras a “transceiver”). The communication unit communicates with anexternal device or a server in a state of being connected in a wired orwireless network. The communication unit may transmit/receive datato/from a server of a hospital or a medical apparatus in the hospitalconnected via a picture archiving and communication system (PACS). Inaddition, the communication unit may perform data communication via theDigital Imaging and Communications in Medicine (DICOM).

The communication unit may perform transmission and reception of datarelated to diagnosis of the object such as an ultrasound image, anultrasonic echo signal, and Doppler data via a network, and may alsoperform transmission and reception of medical images acquired by anothermedical apparatus such as a CT scanner, an MRI apparatus, and an X-rayapparatus. Moreover, the communication unit may receive informationrelated to medical history or treatment schedule of a patient from theserver to diagnose a disease of the object. Furthermore, thecommunication unit may perform data communication with a portableterminal of a doctor or a patient, in addition to the server or medicalapparatus of the hospital.

The communication unit may transmit/receive data to/from a portableterminal in a wired or wireless network. The communication unit mayinclude one or more elements enabling communications with externalapparatuses, for example, a short distance communication module, a wiredcommunication module, and a wireless communication module.

The short distance communication module is a module which is configuredfor communicating with a device located within a predetermined distance.A short distance communication technology according to an exemplaryembodiment may include any of a wireless local area network (LAN),Wi-Fi, Bluetooth, Zigbee, Wi-Fi Direct (WFD), ultra wideband (UWD),infrared data association (IrDA), Bluetooth low energy (BLE), near fieldcommunication (NFC), and/or the like without being limited thereto.

The wired communication module is a module which is configured forcommunicating by using an electric signal or an optical signal, and awired communication technology according to an exemplary embodiment mayinclude any of wired communication technology using a pair cable, acoaxial cable, an optical fiber cable, and an Ethernet cable.

The mobile communication module may transmit/receive a wireless signalto/from at least one of a base, an external terminal, and a server in amobile communication network. Here, the wireless signal may include anyof a voice call signal, a video call signal, or various types of dataaccording to text/multimedia messages transmission.

FIG. 2 is a control block diagram illustrating an ultrasound imagingapparatus, according to an exemplary embodiment.

The ultrasound probe 110 includes a plurality of transducer elements toperform interconversion between electrical signals and ultrasonicsignals and may transmit ultrasonic signals to an object and receiveecho signals reflected by the object. Since ultrasound reflectivityvaries according to medium, the ultrasound probe 110 may acquireinformation which relates to the inside of the object by collectingultrasonic echo signals.

The ultrasound probe 110 may be implemented in any of various wayswithin the technical concept of acquiring volume data of the object. Forexample, when the ultrasound probe 110 has one-dimensional arrangementof elements, the ultrasound probe 110 may acquire volume data inaccordance with a Freehand method. Alternatively, the ultrasound probe110 may acquire volume data by a mechanical method without having a usermanipulation. When the ultrasound probe 110 has a two-dimensionalarrangement of elements, the ultrasound probe 110 may acquire volumedata by controlling the elements.

In particular, when the ultrasound probe 110 receives AC power from anexternal power supply device or an internal power storage device such asa battery, the plurality of transducer elements vibrate to generateultrasonic signals. The ultrasonic signals are irradiated to the object,and echo signals reflected by the object are received by the pluralityof transducer elements. The plurality of transducer elements vibrate inaccordance with the received echo signals, thereby generating currenthaving a frequency corresponding to a vibration frequency.

Referring to FIG. 2, the main body 300 may include a transmit signalgenerator 210, a beamforming unit (also referred to herein as a“beamformer”) 200, a volume data generator 310, a controller 330, astorage unit (also referred to herein as a “storage device” and/or as a“storage”) 340, and an image processor 350.

The transmit signal generator 210 may generate a transmit signal inaccordance with a control instruction from the controller 330 andtransmit the generated transmit signal to the ultrasound probe 110. Inthis regard, the transmit signal refers to a high-pressure electricsignal to vibrate the plurality of transducer elements of the ultrasoundprobe 110.

The beamforming unit 200, which may perform interconversion betweenanalog signals and digital signals, converts the transmit signals(digital signals) generated by the transmit signal generator 210 intoanalog signals or converts echo signals (analog signals) received fromthe ultrasound probe 110 into digital signals which enable communicationbetween the ultrasound probe 110 and the main body 300.

In addition, the beamforming unit 200 may apply time delays to thedigital signals in consideration of positions of vibrators and a focalpoint to overcome a time difference of arrival at the focal point amongultrasonic signals or a time difference of arrival at the transducerelements from the focal point among echo signals.

In particular, under an assumption that a process of concentratingultrasonic signals, which are simultaneously emitted by the plurality oftransducer elements, into a focal point is referred to as focusing, thebeamforming unit 200 may perform transmit focusing, by which theultrasonic signals respectively generated by the transducer elements aresequentially emitted in a predetermined order to remove time differenceof arrival at the focal point among the ultrasonic signals, and receivefocusing, by which the echo signals are simultaneously aligned atrespective transducer elements by using a predetermined time differenceto remove time difference of arrival at the transducer elements amongthe echo signals.

The beamforming unit 200 may be disposed in the main body 300 asillustrated in FIG. 2 or may be installed in the ultrasound probe 110performing functions thereof.

The volume data generator 310 may generate a plurality of volume databefore or while an external stress is applied to the object in responseto a plurality of echo signals received in accordance with a pluralityof ultrasonic signals transmitted by the ultrasound probe 110. In thisregard, the echo signals indicate signals that are processed byexecuting any of various processes by a signal processing unit (alsoreferred to herein as a “signal processor”).

For example, when an echo signal received from an ultrasonic signaltransmitted by the ultrasound probe 110 toward the object before anexternal stress is applied to the object is referred to as a first echosignal, and an echo signal received an ultrasonic signal transmitted bythe ultrasound probe 110 toward the object while the external stress isapplied to the object is referred to as second echo signal, the volumedata generator 310 may generate first volume data corresponding to thefirst echo signal and second volume data corresponding to the secondecho signal.

In this regard, the external stress may be applied to the object usingany of a method of applying stress in a proceeding direction ofultrasound, such as a method of applying static pressure by using a handof an examiner or the ultrasound probe 110, a method of applyinghigh-pressure ultrasound pulse, and a method of applying mechanicalvibration, and/or a method of applying stress in a directionperpendicular to the proceeding direction of ultrasound, such as ashearwave method using a transverse wave, without being limited thereto.

In addition, in order to three-dimensionally visualize the object,two-dimensional (2D) cross-sectional images of the object are acquiredin response to the echo signals received by the ultrasound probe 110,and the 2D cross-sectional images are sequentially stacked in thecorresponding order thereof to generate a set of discretethree-dimensional (3D) alignments. The set of the 3D alignments isvolume data.

Referring to FIGS. 3A and 3B, an example of a volume data will bedescribed. FIG. 3A is a diagram illustrating a plurality of 2Dcross-sectional images. FIG. 3B is a diagram illustrating volume data.

As illustrated in FIG. 3A, a plurality of 2D cross-sectional images F1,F2, F3, . . . , F10 of the object are acquired corresponding to the echosignals received by the ultrasound probe 110. The acquired 2D images F1,F2, F3, . . . , F10 are aligned in a 3D shape in corresponding positionsthereof, and data interpolation of the cross-sectional images isperformed to generate 3D volume data of the object as illustrated inFIG. 3B.

The volume data may be constituted with a plurality of voxels. The term“voxel” is formed from the terms “volume” and “pixel”, and in thisaspect, a “voxel” is equivalent to a pixel which has volume (i.e., a 3Dversion of a pixel). While pixel refers to a single point in a 2D plane,voxel refers to a single point in a 3D space. Thus, a pixel has X and Ycoordinates, whereas a voxel has X, Y, and Z coordinates.

Accordingly, when the volume data is referred to as a group V of voxels,and 3D spatial coordinates indicating the position of the voxel arereferred to as (x, y, z), the voxel may be represented as V_(xyz).

For example, as illustrated in FIG. 3B, a voxel having spatialcoordinates of (0,0,0) may be represented by V₀₀₀, a voxel havingspatial coordinates of (1,0,0) may be represented by V₁₀₀, and a voxelhaving spatial coordinates of (0,1,0) may be represented by V₀₁₀.

In addition, a voxel value va corresponding to a voxel V_(xyz) may berepresented by V(x, y, z)=va. Here, the voxel value va may be a scalarvalue or a vector value, and the volume data may be classified accordingto the type of the voxel.

For example, a voxel value represented by a binary number of 0 or 1 maybe referred to as binary volume data, and a voxel value represented by ameasurable value, such as density and temperature, may be referred to asmulti-valued volume data. In addition, a voxel value represented by avector such as speed or RGB color may be referred to as vector volumedata.

Optical properties of the voxel, such as opacity values and colorvalues, may be calculated using the voxel values. The opacity value maybe calculated using an opacity transfer function that defines therelationship between the voxel values and the opacity values, and thecolor value may be calculated using a color transfer function thatdefines the relationship between the voxel values and the color values.

As described above, a plurality of volume data or voxel values generatedby the volume data generator 310 may be stored in the storage unit 340.According to an exemplary embodiment, the ultrasound probe 110 mayacquire volume data of a brain and the volume data may be stored in thestorage unit 340.

As illustrated in FIG. 2, the storage unit 340 may store data or analgorithm to manipulate the ultrasound imaging apparatus.

For example, the storage unit 340 may store a plurality of volume datagenerated by volume data generator 310. In particular, spatialcoordinates of the voxels and voxel values corresponding thereto may bestored.

The storage unit 340 may also store voxel values, opacity values, andcolor values before and after adjustment by a parameter adjustment unit(also referred to herein as a “parameter adjuster”).

The storage unit 340 may also store image data of a result imagegenerated by the image processor 350, which will be described below.

For example, the storage unit 340 may store algorithms, such as, forexample, any one or more of an algorithm to generate volume data basedon a plurality of 2D cross-sectional images, an algorithm to generateelasticity data based on displacement of the plurality of volume data,an algorithm to align the geometrical positions of the pluralities ofvolume data and elasticity data in a one-to-one correspondence, analgorithm to adjust the opacity value or the voxel value, an algorithmto adjust the color value, and an algorithm to perform volume renderingbased on the volume data.

The storage unit 340 may also store information regarding extraction ofa surface region of the object and data regarding a calculated motionvector, which will be described below.

The storage unit 340 may be implemented as any of a storage deviceincluding a non-volatile memory device such as a read only memory (ROM),a programmable read only memory (PROM), an erasable programmable readonly memory (EPROM), and a flash memory, a volatile memory such as arandom access memory (RAM), a hard disk, or an optical disc. However,the exemplary embodiments are not limited thereto, and any other storageunits well known in the art may also be used.

The display unit 160 may display an ultrasound image generated by theimage processor 350. In particular, the display unit 160 mayindividually or simultaneously display a cross-sectional image or a 3Dimage of the object generated by the image processor 350.

In this case, the display unit 160 display a position of an extractedtarget together with the image. For example, when the ultrasound imagedisplayed in the display unit 160 includes a target, the position of thetarget may be emphasized in the ultrasound image. In particular, thedisplay unit 160 may display a region of the target by using a differentcolor or shade or may display a boundary of the region of the target byusing a different color or shade. Alternatively, the display unit 160may display a marker indicating the position of the target to the user.

A method of displaying the ultrasound image by the display unit 160 willbe described in detail below with reference to the controller 330.

The display unit 160 may also display an ultrasound image generated byframe interpolation according to an exemplary embodiment, which will bedescribed below.

The controller 330 may control the display unit 160 to sequentiallydisplay a plurality of cross-sectional images of the object generated bythe image processor 350.

In particular, the controller 330 may control the display unit 160 tosequentially display the plurality of cross-sectional images of theobject located in a predetermined path in accordance with apredetermined frame rate.

In this regard, the predetermined path refers to not only a linear pathbut also a curved path or a circular path. The path may be determined bya user input or internal calculation of the ultrasound imagingapparatus.

In addition, a distance between the cross-sectional images of the objectand the predetermined frame rate may also be determined by a user inputor internal calculation of the ultrasound imaging apparatus.

When the controller 330 controls the display unit 160 to sequentiallydisplay the plurality of cross-sectional images of the object, thedisplay unit 160 may also display a position of a target on thecross-sectional images of the object.

In addition, the controller 330 may control a surface region extractionunit (also referred to herein as a “surface region extractor”) 400, amotion vector calculation unit (also referred to herein as a “motionvector calculator”) 410, an occluded region motion vector calculationunit (also referred to herein as an “occluded region motion vectorcalculator”) 415, a surface region and motion vector tracking unit (alsoreferred to herein as a “surface region and motion vector tracker”) 420,and a frame interpolation unit (also referred to herein as a “frameinterpolator”) 430, which will be described in detail below.

The image processor 350 may generate an ultrasound image of the objectby using volume data which relates to the object. In this regard, theimage processor 350 may generate not only a 2D ultrasound image of across-section of the object but also generate a 3D ultrasound image.

In order to generate a 3D ultrasound image, the image processor 350 mayperform volume rendering by using volume data. The image processor 350may perform volume rendering of the volume data by using any knownvolume rendering method.

In addition, the image processor 350 may extract a target based on thevolume data.

The image processor 350 may be implemented in any of various ways withinthe technical concept of extracting a target inside the object based onvolume data. For example, the image processor 350 may extract a volumedata region having a brightness within a predetermined range as atarget. Alternatively, the image processor 350 may extract the target bydetermining whether a size of the volume data region having apredetermined brightness is within a predetermined range.

In addition, the image processor 350 may include a rendering unit (alsoreferred to herein as a “renderer”) 351 and an image correction unit(also referred to herein as an “image corrector”) 352.

The rendering unit 351 may perform volume rendering based on 3D volumedata adjusted by the parameter adjustment unit and generate a projectionimage of the object. Particularly, the volume rendering is performed onthe voxel values, the opacity values, and the color values constitutingthe volume data generated before the external stress is applied to theobject. If there is an adjusted value by the parameter adjustment unit,volume rendering is performed by applying the adjusted value thereto.

A method of performing volume rendering by the rendering unit 351 is notlimited. For example, ray casting may be used. Ray casting may beperformed by selecting sample points from the first volume data Vcorresponding to respective pixels of an image, calculating a colorvalue and a transparency value of each of the sample points viainterpolation of adjacent voxels, and calculating color values andtransparency values of the pixels by accumulating the calculated colorvalues and transparency values.

The image correction unit 352 may correct any one or more of brightness,contrast, color, size, and/or direction of the projection imagegenerated by the rendering unit 351.

The image correction unit 352 may transmit the corrected image to thedisplay unit 160 connected to the main body 300 via a wired or wirelesscommunication network. Accordingly, the examiner may check the correctedresult image of the object.

FIG. 4 is a block diagram illustrating the controller 330 of theultrasound imaging apparatus.

The controller 330 may include and control the surface region extractionunit 400, the motion vector calculation unit 410, the occluded regionmotion vector calculation unit 415, the surface region and motion vectortracking unit 420, and the frame interpolation unit 430. Operationsthereof which are related to an exemplary embodiment will be describedin detail with reference to FIGS. 6 and 7.

FIG. 5 is a diagram for describing an occluded region that is hidden bymotion in a 2D image. FIG. 5 is a schematic diagram of a fetus in anultrasound image for convenience of explanation.

As illustrated in FIG. 5, when the object is a fetus, an occluded regionis generated in a 2D ultrasound image by a motion of the fetus. In FIG.5, one arm of the fetus is filled with crosshatched lines which indicatean occluded region. The body of the fetus is partially screened by anarea corresponding to the arm via the motion of the arm of the fetus.Thus, a portion of the body screened by the arm cannot be identifiedusing the 2D ultrasound image. In this aspect, it is difficult tocalculate a motion vector of the occluded portion of the body whilecalculating the motion vector for frame interpolation.

FIG. 6 is a flowchart illustrating a method for controlling anultrasound imaging apparatus by which a surface region and a motionvector of the next frame are not tracked. FIG. 7 is a flowchartillustrating a method for controlling an ultrasound imaging apparatus bywhich a surface region and a motion vector of the next frame aretracked. Hereinafter, an ultrasound imaging apparatus and a method forcontrolling the same according to an exemplary embodiment will bedescribed with reference to FIGS. 4 and 8 to 12.

First, as illustrated in FIG. 6, in operation S100, a surface region ofa 3D image is extracted from volume data.

FIG. 8 is an ultrasound image indicating a surface region to extract asurface region of an object, according to an exemplary embodiment.

As illustrated in FIG. 8, a fetus will be described as the object by wayof example. In a 3D ultrasound image, a portion marked by a line 810 maybe regarded as a frontal surface region of the fetus. In particular, anoutline of the frontal appearance of the fetus is set as the surfaceregion from 3D volume data. It may be understood that an outer surfaceof the 3D image corresponds to the surface region.

The surface region may be a region of the frontal surface of the fetusas illustrated in FIG. 8. Further, any other regions for setting thesurface such as a back surface marked by a line 820 or a side surfacemay be selected.

As illustrated in FIG. 4, the surface region extraction unit 400 of thecontroller 330 extracts the surface region of the object. The surfaceregion extraction unit 400 may extract a surface region required todisplay an image of the object. In particular, the surface regionextraction unit 400 extracts the surface region by selecting a region ofinterest (ROI). A basic method of extracting the surface region entailsextracting a desired surface region from volume data by using a virtualcamera and displaying the extracted surface region on a screen. In thisaspect, a 2D image viewed from the 3D volume data is an image viewedfrom a predetermined position. In addition, the surface of the fetus maybe extracted in the ultrasound image by using support vector machine(SVM)-based texture classification. According to the method ofextracting the surface region of the fetus as described above, a fetusregion is separated from a 3D ultrasound image in order to obtain aclear image of the fetus which is not screened by impurities and toreduce data volume, since a large amount of abdominal walls or floatingmaterials in amniotic fluid are shown in a 3D ultrasound image togetherwith the fetus. In general, a method of separating a fetus region fromthe surroundings in a 3D ultrasound image may include selecting a regionof interest (ROI), extracting a surface, and performing region divisionto remove undesired regions. Thus, the extraction method mayautomatically extract the frontal surface of the fetus from 3Dultrasound volume data by using the SVM-based texture classification.

The surface region extraction unit 400 extracts the surface region ofthe object as described above. However, extraction of the ROI may beimplemented in various ways without limitation.

As illustrated in FIG. 4 and FIG. 6, the motion vector calculation unit410 of the controller 330 calculates a motion vector in the extractedsurface region of the object in accordance with a control by thecontroller 330 in operation S110.

The motion vector refers to a vector which indicates a speed and adirection of a moving object of interest. According to an exemplaryembodiment, the motion vector may be calculated by extracting thesurface region from 3D volume data. By using 3D volume data, motionvectors of respective tissues of the object may be calculated. In thiscase, the motion vector is calculated on the assumption that each tissueof the object linearly moves.

When a first predetermined time is referred to as “t” and a next (i.e.,second) predetermined time is referred to as “t+1”, a vector indicatingthe degree of movement of the object from the first predetermined timeof t to the next time of t+1, i.e., the degree of volume data changebetween the first predetermined time of t and the next time of t+1 tooverlap each other, is the motion vector.

The motion vector calculation unit 410 calculates the motion vector bycomparing volume data which relates to the surface region of the objectat the first predetermined time of t and volume data which relatesthereto at the next time of t+1 through Equation 1 below.

$\begin{matrix}{( {V_{x}^{\prime},V_{y}^{\prime},V_{z}^{\prime}} ) = {\min\limits_{V_{x,}V_{y,}V_{z}}( {\sum\limits_{{({x,y,z})} \in {S{(w)}}}{{{I^{t + 1}( {{x + V_{x}},{y + V_{y}},{z + V_{z}}} )} - {I^{t}( {x,y,z} )}}}} )}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, S is a surface region of the object, the motion vector ofwhich is desired to be calculated, w is one region (window) of thesurface region of volume data, and I is an image of ultrasound volumedata. In addition, t is the first predetermined time and t+1 is the nextpredetermined time as described above, x, y, and z are coordinates ofthe respective axes of the 3D volume data, V_(x), V_(y), and V_(z) areamounts of movement of the object from the first predetermined time of tto the next time of t+1, and V_(x)′, V_(y)′, and V_(z)′ indicate themotion vector.

FIG. 11 will be described in more detail. FIG. 11 illustrates ultrasoundimages showing frame interpolation at a predetermined time, according toan exemplary embodiment.

As illustrated in FIG. 11, when image {circle around (1)} is referred toas an ultrasound image at a time of t, and image {circle around (6)} isreferred to as an ultrasound image at a time of t+1, frame interpolationis performed after predicting movement of the object by calculating amotion vector between the images {circle around (1)} and {circle around(6)}.

In Equation 1, the motion vector of one region w instead of the entireregion of a corresponding surface region S (also referred to herein as a“subregion w”) of the image is calculated. When the movement from thetime of t to the time of t+1 is changed by V_(x), V_(y), and V_(z), aposition which has changed from initial coordinates x, y, and z byV_(x), V_(y), and V_(z) is illustrated in an image at the time of t+1.Thus, a motion vector V_(x)′, V_(y)′, and V_(z)′ corresponding to anamount of movement change may be found by calculating a differencebetween a position which corresponds to the image at the time of t+1 anda position which corresponds to the image at the time of t as a vectordifference and adding up the vector difference. As a minute value, theamount of movement change V_(x), V_(y), and V_(z) of the objectgenerated from the time of t to the time of t+1 is calculated to beminimized.

Frame interpolation is performed by forming images between the time of tand the time of t+1 by using the motion vector calculated according tothe aforementioned method, and a detailed description thereof will begiven below.

While calculating the motion vector, a motion vector of an occludedregion is also calculated. As described above with reference to FIG. 5,an occluded region is generated in the extracted surface region of theobject according to the motion of the object or change in movement ofthe object when a 2D image is displayed. In order to perform frameinterpolation to which the motion vector of the occluded region isreflected, the motion vector of the occluded region is also calculated.

As illustrated in FIG. 4 and FIG. 6, the occluded region motion vectorcalculation unit 415 within the motion vector calculation unit 410 iscontrolled by the controller 330 to calculate the motion vector of theoccluded region in operation S115, which will be described withreference to FIGS. 9A and 9B.

Referring to FIGS. 9A and 9B, an ultrasound image having an occludedregion generated at the time of t as described above with reference toFIG. 5 is illustrated in FIG. 9A, and an ultrasound image in which themotion of the object is changed at the time of t+1 is illustrated inFIG. 9B. The occluded region may be extracted from a difference betweendata at the time of t and data at the time of t+1. In FIG. 9A, since thefetus is putting one arm on the body, an occluded region is caused bythe arm with respect to the body. In FIG. 9B, since the fetus isstretching the arm, a motion vector of the body corresponding to theoccluded region may be calculated by using the difference between thetwo ultrasound images.

Hereinafter, the occluded region will be described with reference toEquation 2.{circle around (1)}S _(t) =P(I ^(t)){circle around (2)}S _(t+1) =P(I ^(t+1)){circle around (3)}S′=XoR(S _(t) ,S _(t+1)){circle around (4)}S _(t) ′=S _(t) ∪S′{circle around (5)}S _(t+1) ′=S _(t+1) ∪S′  Equation 2

In Equation 2, S is a surface region of the object, and S′ is anoccluded region. Equation 2-{circle around (1)} is an equation whichrelates to an image of ultrasonic volume data in the surface region ofthe object of the time of t, and Equation 2-{circle around (2)} is anequation which relates to an image of ultrasonic volume data in thesurface region of the object at the time of t+1. Equation 2-{circlearound (3)} is an equation for calculating the occluded region in thesurface region by using Equation 2-{circle around (1)} and Equation2-{circle around (2)}. An exclusive OR (XoR) region of S_(t) and S_(t+1)corresponds to the occluded region. Equation 2-{circle around (4)} is anequation for calculating a motion vector of the surface region having anoccluded region at the time of t and corresponds to an union of thesurface region S_(t) and the occluded region S′. Equation 2-{circlearound (5)} is an equation for calculating a motion vector of thesurface region having an occluded region at the time of t+1 andcorresponds to a union between the surface region S_(t+1) and theoccluded region S′. Thus, the motion vector of the occluded region maybe calculated by using Equation 2-{circle around (4)} and Equation2-{circle around (5)} as described above with reference to thecalculation of the motion vector.

As described above, the motion vector calculation unit 410 and theoccluded region motion vector calculation unit 415 calculate the motionvector which includes the motion vector of the occluded region of theobject in the ultrasound image based on the extracted surface region ofthe object, and data which relates to the calculated motion vector maybe stored in the storage unit 340, which will be described below.

As illustrated in FIG. 4 and FIG. 6, the frame interpolation unit 430 ofthe controller 330 performs frame interpolation on the surface region byusing the motion vector calculated in the surface region of the objectby a control of the controller 330 in operation S120.

FIG. 11 illustrates ultrasound images which indicate a frameinterpolation at a predetermined time, according to an exemplaryembodiment.

As illustrated in FIG. 11, in ultrasound images of the fetus, the motionvector between the time of t and the time of t+1 is calculated, andframe interpolation is performed between the time of t and the time oft+1. When image {circle around (1)} is referred to as an image at thetime of t, and image {circle around (6)} is referred to as an image atthe time of t+1, images therebetween are images generated by frameinterpolation based on the calculated motion vector. FIG. 11 illustratesa relatively small number of images generated by frame interpolation forconvenience of explanation. In actual frame interpolation, more imagesmay be generated, and a relatively short time interval may be usedbetween successive generations of images, thereby generating a naturalimage.

According to a frame interpolation method according to an exemplaryembodiment, a natural real time multifocal ultrasound image may beprovided by changing a frame rate by inserting interpolated frames.

According to the frame interpolation method, the frame rate of a finalimage may be increased by additionally inserting virtual images betweentwo image pairs of different times, thereby providing a natural image,i.e., moving image.

FIG. 10A is a diagram for describing virtual images generated by frameinterpolation.

FIG. 10A illustrates m virtual images generated by an interpolationmethod and inserted between an n^(th) frame and an (n+1)^(th) frameamong n frames of an image. FIG. 10B illustrates examples of virtualimages generated by frame interpolation as described in FIG. 10A. Byinserting the generated virtual images between the n^(th) frame and the(n+1)^(th) frame, a motion of the fetus may be naturally displayed.

First, referring to FIG. 10A, when a linear interpolation method isused, a display time of an image at the n^(th) frame and coordinates ofa pixel of the image are referred to as (t_(n), y_(n)), and a displaytime of an image at the (n+1)^(th) frame and coordinates of a pixel ofthe image are referred to as (t_(n+1), y_(n+1)). In this case, a displaytime of the j^(th) virtual image and coordinates of a pixel in the imageamong m virtual images inserted between the n^(th) frame and the(n+1)^(th) frame may be defined as (t_(aj), y_(aj)). All data whichrelates to the m virtual images may be generated by applying an equationwhich relates to virtual image insertion to all pixels of each of the mvirtual images inserted between the n^(th) frame and the (n+1)^(th)frame. The equation is well known in the art, and thus a detaileddescription thereof will not be given herein.

As illustrated in FIG. 10B, a natural ultrasound image of the fetus maybe generated by inserting virtual images between the n^(th) frame andthe (n+1)^(th) frame. According to an exemplary embodiment, frameinterpolation may be performed by using the calculated motion vector ofthe surface region of the object.

Hereinafter, frame interpolation will be described with reference to thefollowing equations.

$\begin{matrix}{\mspace{79mu}\frac{{( {N - k} )*a} + {k*b}}{N}} & {{Equation}\mspace{14mu} 3} \\{\mspace{79mu}{{{◯1}\mspace{14mu}{I^{t}( {{x + {\frac{k}{N}*V_{x}}},{y + {\frac{k}{N}*V_{y}}},{z + {\frac{k}{N}*V_{z}}}} )}}{{◯2}\mspace{14mu}{I^{t + 1}( {{x - {\frac{( {N - k} )}{N}*V_{x}}},{y - {\frac{( {N - k} )}{N}*V_{y}}},{z - {\frac{( {N - k} )}{N}*V_{z}}}} )}}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

When I^(t) is referred to as an image of ultrasonic volume data at thetime of t, and I^(t+1) is referred to as an image of ultrasonic volumedata at the time of t+1, linear interpolation may be represented byEquation 3.

In Equation 3, N is the number of interpolation steps (the number ofimages interpolated between the time of t and the time of t+1, i.e., thenumber of images to be generated), k is an ordinal number of an imageamong the interpolated images, “a” is image interpolation from the timeof t to the time of t+1, and “b” is image interpolation from the time oft+1 to the time of t.

As a motion vector with respect to a variation of the movement of theobject with time, a variation at the time of t may be represented by (0,0, 0), a variation at a time of t+0.5 is may be represented by (V_(x)/2,V_(y)/2, V_(z)/2), and a variation at the time of t+1 may be representedby (V_(x), V_(y), V_(z)). Thus, interpolated images of the image ofultrasonic volume data with time may be I^(t)(x, y, z) at the time of t,I^(t)(x+V_(x)/2, y+V_(y)/2, z+V_(z)/2) at the time of t+0.5, andI^(t)(x+V_(x), y+V_(y), z+V_(z)) at the time of t+1.

A time interval of the frame interpolation is Δt=k/N. Here, Δt is a veryshort time which generally falls within a range of between several tensof milliseconds to several hundreds of milliseconds.

After Δt, general equations of the interpolated image may be representedby Equation 4-{circle around (1)} and Equation 4-{circle around (2)}.Equation 4-{circle around (1)} may be referred to as “a” which indicatesimage interpolation from the time of t to the time of t+1, and Equation4-{circle around (2)} may be referred to as “b” which indicates imageinterpolation from the time of t+1 to the time of t.

Thus, an equation for calculating an interpolated image after Δt may beobtained by substituting equations of a and b into Equation 3. This maybe interpreted as an average between a and b in the linearinterpolation.

The frame interpolation unit 430 may perform frame interpolation on thesurface region image of the object by using the aforementioned imageinterpolation method by a control of the controller 330. However, theimage interpolation method is not limited thereto, and various othermethods may also be used.

Hereinafter, a method of determining a surface region at a predeterminedframe by tracking a motion vector of the surface region of thepredetermined frame by using data which relates to a calculated motionvector of a surface region with respect to a preceding frame will bedescribed.

FIG. 7 is a flowchart illustrating a method for controlling anultrasound imaging apparatus by which a surface region and a motionvector of the predetermined frame are tracked. In this aspect, thepredetermined frame is referred to herein as the “next” frame becausethe method entails using data which relates to the preceding frame.

The surface region and motion vector of the next frame are tracked sincean amount of calculation increases when the surface region is extractedfrom volume data at each frame and the motion vector is calculatedtherefrom. The amount of calculation may be reduced by tracking thesurface region and the motion vector of the next frame within apredetermined range based on data stored in the storage unit 340 inoperation S130. In particular, a region of the motion vector of the nextframe is estimated within the range of the previous motion vector.

As illustrated in FIG. 7, in operation S150, the surface region andmotion vector tracking unit 420 in the controller 330 determines whetherthe surface region and the motion vector of the next frame are within apredetermined (stored) range of the surface region and the motion vectorin images generated by frame interpolation performed on the surfaceregion of the volume data of the object by a control of the controller330. When the surface region and the motion vector of the next frame arewithin the predetermined range, in operation S140, the motion vector iscalculated within the range. In particular, a variation of movementwithin a range of vector quantities of the motion vector on the previoussurface region is calculated as a motion vector. However, when thesurface region and the motion vector of the next frame are not withinthe predetermined range, in operation S145, the motion vector iscalculated in the entire range according to the control illustrated inFIG. 6 without considering the range.

As described above, the tracking of the surface region and the motionvector of the next frame is within the scope of the present disclosureand may be optionally applied to exemplary embodiments of the presentdisclosure.

As described above, the method for controlling the ultrasound imagingapparatus may include extracting a surface region, calculating a motionvector of the surface region, performing frame interpolation by usingthe calculated motion vector, calculating a motion vector of an occludedregion while calculating the motion vector of the surface region, andtracking a surface region and a motion vector of the next frame, asillustrated in FIG. 6 and FIG. 7.

FIG. 12 illustrates ultrasound images indicating frame interpolation atconsecutive times, according to an exemplary embodiment.

In FIG. 12, a time interval between frames is set as 1 second. Asillustrated in FIG. 12, frames may be classified into frames at 1 sec,frames at 2 sec, and frames at 3 sec.

At 1 sec, frame interpolation according to an exemplary embodiment isperformed between image {circle around (1)} and image {circle around(6)} as described above. At 2 sec, frame interpolation is performedbetween image {circle around (6)} obtained at 1 sec, as a startingimage, and image {circle around (2)}. At 3 sec, frame interpolation isperformed between image {circle around (2)} obtained at 2 sec, as astarting image, and image {circle around (5)}. Thus, natural images maybe generated by frame interpolation performed on the surface region ofthe object.

As illustrated in FIGS. 6 and 7, after the frame interpolation isperformed, in operation S160, the rendering unit 351 of the imageprocessor 350 performs volume rendering, and the generated ultrasoundimage is displayed on the display unit 160.

According to an exemplary embodiment, the ultrasound imaging apparatusextracting a surface region of an object from volume data, performingframe interpolation on the extracted surface region of the object tocalculate a motion vector, and the method of controlling the ultrasoundimaging apparatus are described above.

As is apparent from the above description, according to the ultrasoundimaging apparatus and the method of controlling the same according to anexemplary embodiment, the occluded region generated in a 2D image may beremoved, and the amount of calculation of the motion vector of 3D volumedata may be reduced.

Although a few exemplary embodiments have been shown and described, itwill be appreciated by those of skill in the art that changes may bemade in these exemplary embodiments without departing from theprinciples and spirit of the present inventive concept, the scope ofwhich is defined in the claims and their equivalents.

What is claimed is:
 1. An ultrasound imaging apparatus comprising: avolume data generator configured to acquire volume data which relates toan object; a surface region extractor configured to extract a surfaceregion of the object based on the acquired volume data; and a frameinterpolator configured to perform frame interpolation on the extractedsurface region of the object.
 2. The ultrasound imaging apparatusaccording to claim 1, further comprising a motion vector calculatorconfigured to calculate a motion vector in the extracted surface regionof the object.
 3. The ultrasound imaging apparatus according to claim 2,wherein the motion vector calculator comprises an occluded region motionvector calculator configured to calculate a motion vector of an occludedregion.
 4. The ultrasound imaging apparatus according to claim 3,wherein the occluded region includes a region which corresponds to atime difference between a first predetermined time and a secondpredetermined time in the surface region of the object.
 5. Theultrasound imaging apparatus according to claim 4, wherein the motionvector calculator is further configured to calculate the motion vectorby comparing volume data which relates to the first predetermined timewith volume data which relates to the second predetermined time.
 6. Theultrasound imaging apparatus according to claim 3, wherein the occludedregion includes a region generated when the frame interpolation isperformed.
 7. The ultrasound imaging apparatus according to claim 3,wherein the occluded region motion vector calculator is furtherconfigured to calculate the motion vector of the occluded regionsimultaneously with calculating the motion vector in the surface regionof the object.
 8. The ultrasound imaging apparatus according to claim 2,wherein the motion vector calculator comprises a surface region andmotion vector tracker configured to track a surface region and a motionvector of a predetermined frame.
 9. The ultrasound imaging apparatusaccording to claim 8, wherein the surface region and motion vectortracker is further configured to track the surface region and the motionvector of the predetermined frame based on data which relates to theextracted surface region and the calculated motion vector.
 10. Theultrasound imaging apparatus according to claim 2, wherein the motionvector calculator is further configured to calculate a motion vector ofa subregion of a frame.
 11. The ultrasound imaging apparatus accordingto claim 1, wherein the surface region extractor is further configuredto extract a surface region of at least one from among an outline of afetus and an organ comprising a heart.
 12. A method for controlling anultrasound imaging apparatus, the method comprising: acquiring volumedata which relates to an object; extracting a surface region of theobject based on the acquired volume data; and performing frameinterpolation on the extracted surface region of the object.
 13. Themethod according to claim 12, further comprising calculating a motionvector in the extracted surface region of the object.
 14. The methodaccording to claim 13, wherein the calculating the motion vectorcomprises calculating a motion vector of an occluded region.
 15. Themethod according to claim 14, wherein the calculating the motion vectorof the occluded region is performed simultaneously with calculating themotion vector in the surface region of the object.
 16. The methodaccording to claim 13, wherein the calculating the motion vector isperformed by calculating a motion vector by comparing volume data whichrelates to a first predetermined time with volume data which relates toa second predetermined time.
 17. The method according to claim 16,wherein the calculating the motion vector in the surface region of theobject comprises tracking a surface region and a motion vector of apredetermined frame.
 18. The method according to claim 17, wherein thetracking the surface region and the motion vector of the predeterminedframe is performed by tracking a surface region and a motion vector ofthe predetermined frame based on data which relates to the extractedsurface region and the calculated motion vector.
 19. The methodaccording to claim 13, wherein the calculating the motion vector isperformed by calculating a motion vector of a subregion of a frame. 20.The method according to claim 12, wherein the object includes a fetus,and the extracting the surface region of the object is performed byextracting a surface region of at least one from among an outline of thefetus and an organ comprising a heart.